Stable propagating waves and wake fields in relativistic electromagnetic plasma are investigated. The incident electromagnetic field has a finite initial constant amplitude meanwhile the longitudinal momentum of elect...Stable propagating waves and wake fields in relativistic electromagnetic plasma are investigated. The incident electromagnetic field has a finite initial constant amplitude meanwhile the longitudinal momentum of electrons is taken into account in the problem. It is found that in the moving frame with transverse wave group velocity the stable propagating transverse electromagnetic waves and longitudinal plasma wake fields can exist in the appropriate regime of plasma.展开更多
To address the complex seismic response of long tunnels longitudinally crossing heterogeneous geological formations,this study proposes a three-dimensional SV-wave oblique-incidence input method that accounts for the ...To address the complex seismic response of long tunnels longitudinally crossing heterogeneous geological formations,this study proposes a three-dimensional SV-wave oblique-incidence input method that accounts for the initial disturbance of the wave field induced by geological heterogeneity.The method transforms equivalent twodimensional free-field responses into equivalent nodal forces applied at the boundaries of a 3D numerical model.A longitudinally heterogeneous“hard-soft-hard”site and tunnel system is established,in which the surrounding rock is modeled using the Mohr-Coulomb constitutive law,while the concrete lining is described by the concrete damaged plasticity model.The deformation patterns and failure mechanisms of the site-tunnel system under SV-wave excitation are systematically investigated.The results indicate that seismic damage under SV-wave loading is mainly concentrated in the soft-rock region.Failure of the soft surrounding rock induces pronounced sliding of the overlying hard rock,and the tunnel suffers severe damage due to the combined effects of soft-rock failure and strong ground shaking.Parametric analyses further show that smaller impedance ratios,larger soft-rock widths,and larger incidence angles significantly intensify the seismic response of the tunnel.The findings of this study provide valuable insights for the seismic design of tunnels crossing longitudinally heterogeneous geological formations.展开更多
In mining engineering,dynamic loads acting on the surrounding rock induce irreversible damage.The damage is further exacerbated by water exudation from filling bodies or groundwater in the surrounding rock.Understandi...In mining engineering,dynamic loads acting on the surrounding rock induce irreversible damage.The damage is further exacerbated by water exudation from filling bodies or groundwater in the surrounding rock.Understanding the propagation and energy characteristics of stress waves in damaged surrounding rock is essential for improving the stability of underground structures.Hence,in this study,an improved triaxial Split Hopkinson Pressure Bar(SHPB)testing system was used to prepare four sets of impact-damaged and water-soaked specimens with varying length-to-diameter ratios in the laboratory,followed by dynamic triaxial compression testing.Test results indicate that,following dynamic impact and water soaking,the propagation of stress waves in rock is altered.Compared with intact specimens,impact-damaged and water-soaked specimens(IDWS)show a reduction in both transmission and reflection coefficients,thereby enhancing their energy absorption capacity and decreasing transmitted and reflected energy.The length(length-to-diameter ratio)of the specimen and the peak of the incident wave also affect stress wave propagation.Under the same incident peak value,the transmission coefficient increases with larger length-to-diameter ratios,whereas the reflection coefficient decreases.Similarly,the energy carried by the stress wave is influenced by specimen length:as the length grows,the energy absorbed per unit volume declines.When using energy absorbed per unit volume to characterize the dynamic triaxial strength of rock,the length-to-diameter ratio effect on strength is not pronounced.展开更多
Most existing path planning approaches rely on discrete expansions or localized heuristics that can lead to extended re-planning,inefficient detours,and limited adaptability to complex obstacle distributions.These iss...Most existing path planning approaches rely on discrete expansions or localized heuristics that can lead to extended re-planning,inefficient detours,and limited adaptability to complex obstacle distributions.These issues are particularly pronounced when navigating cluttered or large-scale environments that demand both global coverage and smooth trajectory generation.To address these challenges,this paper proposes a Wave Water Simulator(WWS)algorithm,leveraging a physically motivated wave equation to achieve inherently smooth,globally consistent path planning.In WWS,wavefront expansions naturally identify safe corridors while seamlessly avoiding local minima,and selective corridor focusing reduces computational overhead in large or dense maps.Comprehensive simulations and real-world validations-encompassing both indoor and outdoor scenarios-demonstrate that WWS reduces path length by 2%-13%compared to conventional methods,while preserving gentle curvature and robust obstacle clearance.Furthermore,WWS requires minimal parameter tuning across diverse domains,underscoring its broad applicability to warehouse robotics,field operations,and autonomous service vehicles.These findings confirm that the proposed wave-based framework not only bridges the gap between local heuristics and global coverage but also sets a promising direction for future extensions toward dynamic obstacle scenarios and multi-agent coordination.展开更多
Convection in a horizontal fluid layer heated from below is one of models for studying patterns of convection in binary fluid mixtures and has been extensively studied. In this article, the convection structures in a ...Convection in a horizontal fluid layer heated from below is one of models for studying patterns of convection in binary fluid mixtures and has been extensively studied. In this article, the convection structures in a rectangular cell were investigated for the aspect-ratio Г= 12 and the separation ratio ψ = -0.47. Simulations were preformed by solving the hydrodynamic equations using the SIMPLE method. A Counter Propagating Wave （CPW） state was found in binary fluid convection with a periodically horizontal motion of defects, and the pattern dynamics was further discuss.展开更多
To address the problem of subdividing inflexible rectangular grid models and their poor definition of velocity interfaces,we propose a complex structure triangular net for a minimum traveltime ray tracing global algor...To address the problem of subdividing inflexible rectangular grid models and their poor definition of velocity interfaces,we propose a complex structure triangular net for a minimum traveltime ray tracing global algorithm.Our procedure is：（1） Subdivide a triangle grid based on the Delaunay triangular subdivision criterion and the relationships of the points,lines,and the surfaces in the subdividing area.（2） Define the topology relationships and related concepts of triangular unit ray tracing.（3） The source point and wave arrival points at any time compose the propagating plane wave and the minimum traveltime and secondary source positions are calculated during the plane wave propagation.We adopt the hyperbolic approximation global algorithm for secondary source retrieving.（4） By minimum traveltime ray tracing,collect the path from receiver to source points with the neighborhood point＇s traveltime and the direction of the secondary source.Numerical simulation examples are given to test the algorithm.The results show that the triangular net ray tracing method demonstrates model subdivision flexibility,precise velocity discontinuity interfaces,and accurate computations.展开更多
The dynamical response of spin-S(S=1, 3/2, 2, 3) Ising ferromagnet to the plane propagating wave, standing magnetic field wave and uniformly oscillating field with constant frequency are studied separately in two dime...The dynamical response of spin-S(S=1, 3/2, 2, 3) Ising ferromagnet to the plane propagating wave, standing magnetic field wave and uniformly oscillating field with constant frequency are studied separately in two dimensions by extensive Monte Carlo simulation. Depending upon the strength of the magnetic field and the value of the spin state of the Ising spin lattice two different dynamical phases are observed. For a fixed value of S and the amplitude of the propagating magnetic field wave the system undergoes a dynamical phase transition from propagating phase to pinned phase as the temperature of the system is cooled down. Similarly in case with standing magnetic wave the system undergoes dynamical phase transition from high temperature phase where spins oscillate coherently in alternate bands of half wavelength of the standing magnetic wave to the low temperature pinned or spin frozen phase. For a fixed value of the amplitude of magnetic field oscillation the transition temperature is observed to decrease to a limiting value as the value of spin S is increased. The time averaged magnetisation over a full cycle of the magnetic field oscillation plays the role of the dynamic order parameter. A comprehensive phase boundary is drawn in the plane of magnetic field amplitude and dynamic transition temperature. It is found that the phase boundary shrinks inwards for high value of spin state S.Also in the low temperature(and high field) region the phase boundaries are closely spaced.展开更多
Theoretical description of the wave propagation in an elliptical cylinder multilayer structure under the conditions of H polarization and E polarization is presented. A transfer matrix method has been developed for el...Theoretical description of the wave propagation in an elliptical cylinder multilayer structure under the conditions of H polarization and E polarization is presented. A transfer matrix method has been developed for elliptical cylinder waves. The formulas of reflection and transmission coefficients for an elliptical cylinder multilayer structure are driven. Reflection and transmission coefficients of elliptical cylinder waves by a single elliptical cylinder interface is presented. The obtained formulas can be generalized to the cold plasma filled structures and thus the obtained results in the limit of circular cylinder structures are investigated.展开更多
By performing one-dimensional （l-D） hybrid simulations, we analyze in detail the parametric instabilities of the Alfv^n waves with a spectrum in a low beta plasma. The parametric instabilities experience two stages....By performing one-dimensional （l-D） hybrid simulations, we analyze in detail the parametric instabilities of the Alfv^n waves with a spectrum in a low beta plasma. The parametric instabilities experience two stages. In the first stage, the density modes are excited and immediately couple with the pump Alfv6n waves. In the second stage, each pump Alfv^n wave decays into a density mode and a daughter Alfv6n mode similar to the monochromatic cases. Ftlrthermore, the proton velocity beam will also be formed after the saturation of the parametric instabilities. When the plasma beta is high, the parametric decay in the second stage will be strongly suppressed.展开更多
Traffic engineering such as tunnels in various altitudinal gradient zone are at risk of accidental explosion,which can damage personnel and equipment.Accurate prediction of the distribution pattern of explosive loads ...Traffic engineering such as tunnels in various altitudinal gradient zone are at risk of accidental explosion,which can damage personnel and equipment.Accurate prediction of the distribution pattern of explosive loads and shock wave propagation process in semi-enclosed structures at various altitude environment is key research focus in the fields of explosion shock and fluid dynamics.The effect of altitude on the propagation of shock waves in tunnels was investigated by conducting explosion test and numerical simulation.Based on the experimental and numerical simulation results,a prediction model for the attenuation of the peak overpressure of tunnel shock waves at different altitudes was established.The results showed that the peak overpressure decreased at the same measurement points in the tunnel entrance under the high altitude condition.In contrast,an increase in altitude accelerated the propagation speed of the shock wave in the tunnel.The average error between the peak shock wave overpressure obtained using the overpressure prediction formula and the measured test data was less than15%,the average error between the propagation velocity of shock waves predicted values and the test data is less than 10%.The method can effectively predict the overpressure attenuation of blast wave in tunnel at various altitudes.展开更多
The acoustic wave propagation in gas-saturated double-porosity materials composed of a microporous matrix and mesopores with arrays of plate-type resonators is investigated.A macroscopic description,established with t...The acoustic wave propagation in gas-saturated double-porosity materials composed of a microporous matrix and mesopores with arrays of plate-type resonators is investigated.A macroscopic description,established with the two-scale asymptotic homogenization method,evidences the combined effect of inner resonances on the acoustic properties of the respective effective visco-thermal fluid.One type of resonance originates from strong pore-scale fluid-structure interaction,while the other one arises from pressure diffusion.These phenomena respectively cause weakly and highly damped resonances,which are activated by internal momentum or mass sources,and can largely influence,depending on the material's morphology,either the effective fluid's dynamic density,compressibility,or both.We introduce semi-analytical models to illustrate the key effective properties of the studied multiscale metamaterials.The results provide insights for the bottom-up design of multiscale acoustic metamaterials with exotic behaviors,such as the negative,very slow,or supersonic phase velocity,as well as sub-wavelength bandgaps.展开更多
The southern part of East Siberia(SES)is highly vulnerable to flooding caused by the extreme precipitation events(EPEs)during summer.Building on previously detected EPEs in SES and Mongolia,we examined wave propagatio...The southern part of East Siberia(SES)is highly vulnerable to flooding caused by the extreme precipitation events(EPEs)during summer.Building on previously detected EPEs in SES and Mongolia,we examined wave propagation patterns for two periods:1982-98 and 1999-2019.Our analysis revealed distinct wave train configurations and geopotential anomalies preceding EPEs,with an increase in wave activity flux across the Northern Hemisphere,followed by a subsequent decrease during EPEs.Consequently,Eastern Siberia has experienced a significant rise in wave activity.Based on geopotential anomalies over Central Siberia accompanying EPEs,we identified two main types.The first,the ridge type,is predominant during the first period and features a meridional contrast with a positive geopotential(and temperature)anomaly over Central Siberia and a negative anomaly over the subtropical regions along the same longitude.The second type,termed the trough type,is more typical for the second period.It involves either a negative geopotential anomaly or the zonal proximity of positive and negative geopotential anomalies over Central Siberia.The trough type,marked by zonally oriented anomalies in geopotential and temperature,results in a more pronounced temperature decrease before EPEs and significant zonal temperature contrasts.Further,it is related to more stationary waves over Northern Eurasia,with persistent positive geopotential anomalies over Europe linked to quasi-stationary troughs over Central Siberia and positive anomalies east of Lake Baikal.Our findings align with shifts in boreal summer teleconnection patterns,reflecting significant changes in wave propagation patterns that have occurred since the late 1990s.展开更多
In this paper,enhanced near-field shock wave propagation in underwater explosion is achieved by introducing a fragile air-tube under the explosive.Firstly,based on the ALE algorithm in the ANSYS/LS-DYNA software,a num...In this paper,enhanced near-field shock wave propagation in underwater explosion is achieved by introducing a fragile air-tube under the explosive.Firstly,based on the ALE algorithm in the ANSYS/LS-DYNA software,a numerical model integrating the water,the air,the explosive,and the air-tube is developed.Comparative discussion for explosion with air-tube in the air,as well as explosion in the water without air-tube,is made to highlight the distinct energy attenuation mechanism due to the introduction of the air-tube.Then,the influence of the tube geometry,as well as evolving structural boundaries,on the explosive process is discussed exhaustively.The results indicate that the air-tube acts as a shock focusing apparatus,significantly altering explosion flow dynamics.Tube damage mode relies on tube geometrical size.Time-refreshed structural boundary affects the position the fluid flowing into the air-tube,which in turn plays an impact on the bubble pattern and energy distribution near the tube outlet.Enhanced outlet pressure is strengthened along with the decrease of the outlet radius,cross-section height ratio and tube thickness.These insights offer valuable guidance for optimizing underwater explosion and possess prospectively scientific and practical significance.展开更多
Global acoustic simulations are significant in revealing the internal and physical structure of the Earth.However,due to the limited flexibility of grids and the difficulties in handling boundaries,the traditional fin...Global acoustic simulations are significant in revealing the internal and physical structure of the Earth.However,due to the limited flexibility of grids and the difficulties in handling boundaries,the traditional finite-difference method(FDM)is usually less used in global simulations.Nevertheless,these issues can be well resolved by employing a multi-block structured grid to discretize circular regions.In this paper,we propose an O-H grid approach to partition the circular region and utilize the curvilinear grid finite-difference method(CGFDM)to solve the acoustic wave equation within this circular domain.By appropriately stretching the grid,the interconnections between each grid block are sufficiently smooth for stable information exchange.To verify the efficacy of this method,we conducted three numerical experiments,by comparing results with alternative approaches.Our test results demonstrate good agreement between our findings and the reference solutions.Since the proposed algorithm can effectively solve wave propagation problems in circular regions,it can contribute to 2D global simulation,particularly in interpreting the Earth’s interior.展开更多
With the application of hypervelocity weapons in warfare,comprehensively evaluating their destructive effects is of particular interest for protective engineering.Existing studies mostly focused on the depth of penetr...With the application of hypervelocity weapons in warfare,comprehensively evaluating their destructive effects is of particular interest for protective engineering.Existing studies mostly focused on the depth of penetration by hypervelocity projectile,while investigation on stress waves associated with hypervelocity penetration was very limited.To clarify the generation and propagation of stress waves in concrete targets induced by hypervelocity projectile penetration,in the present study,six spherical projectile penetration tests on concrete targets were firstly conducted with projectile velocity ranged from 1875 m/s to 3940 m/s,in which the stress waves were carefully measured by the PVDF transducers.Then corresponding numerical models were developed and validated,and based on the validated numerical model the mechanisms of generation and propagation of stress waves were clarified.It was found that the stress waves observed during hypervelocity penetration are generated by the continuous interactions of projectile and target during penetration,and have unique characteristics such as the directionality and the"two peaks"phenomenon when compared with the stress waves generated by charge explosion.Finally,the effects of projectile velocity,projectile material,and target strength on the stress waves below the penetration depth we re numerically investigated,and two important indexes for evaluating the stress waves by hypervelocity penetration were proposed.展开更多
Coastal near-inertial waves are usually generated by storms passing offshore and/or nearshore,and modified by the presence of the coast.They can modify coastal currents and upper-layer velocity structures,thereby affe...Coastal near-inertial waves are usually generated by storms passing offshore and/or nearshore,and modified by the presence of the coast.They can modify coastal currents and upper-layer velocity structures,thereby affecting material transport and ecosystem processes in the coastal region.The propagation characteristics of coastal near-inertial waves(CNIWs)are investigated in this study by using the Regional Ocean Circulation Modelling System(ROMS)model,forced by wind fields incorporating an idealized wind model around the typhoon center and ERA5 wind reanalysis data from ECMWF(European Center of Meteorological Weather Forecasting)beyond the typhoon center,and with realistic bathymetric data near the Guangdong coast,China.Spatial coherence analysis reveals that near-inertial energy propagates shoreward and upward along middle layers,guided by the topography.Near the coast,energy is transmitted offshore due to the presence of the coastal wall.Calculations of energy transport flux and group velocity further elucidate the wave propagation patterns,showing that near-inertial energy propagates onshore during the typhoon passage and offshore afterward.A two-layer structure of energy flux,separated by the thermocline,is identified,with variations observed between successive inertial periods.The sensitivity of CNIWs’propagation to typhoon parameters is examined through 12 experiments.A 10%increase in maximum wind velocity(V_(max)),radius of maximum wind(R_(max)),and typhoon translation speed()lead to respective changes in energy flux(−5%to+25%)and group velocity(−1%to+0.4%),highlighting their impacts on the CNIWs’energy fluxes.This study is of importance to coastal dynamics and disaster management.展开更多
Rock discontinuities such as joints widely exist in natural rock masses,and wave attenuation through rock masses is mainly caused by discontinuities.The displacement discontinuity model(DDM)has been widely used in the...Rock discontinuities such as joints widely exist in natural rock masses,and wave attenuation through rock masses is mainly caused by discontinuities.The displacement discontinuity model(DDM)has been widely used in theoretical and numerical analysis of wave propagation across rock discontinuity.However,the circumstance under which the DDM is applicable to predict wave propagation across rock discontinuity remains poorly understood.In this study,theoretical analysis and ultrasonic laboratory tests were carried out to examine the theoretical applicability of the DDM for wave propagation,where specimens with rough joints comprising regular rectangular asperities of different spacings and heights were prepared by 3D printing technology.It is found that the theoretical applicability of the DDM to predict wave propagation across rock discontinuity is determined by three joint parameters,i.e.the dimensionless asperity spacing(L),the dimensionless asperity height(H)and the groove density(D).Through theoretical analysis and laboratory tests,the conditions under which the DDM is applicable are derived as follows:and,.With increase in the groove density,the thresholds of the dimensionless asperity spacing and the dimensionless asperity height show a decreasing trend.In addition,the transmission coefficient in the frequency domain decreases with increasing groove density,dimensionless asperity spacing or dimensionless asperity height.The findings can facilitate our understanding of DDM for predicting wave propagation across rock discontinuity.展开更多
3D traveltime calculation is widely used in seismic exploration technologies such as seismic migration and tomography. The fast marching method （FMM） is useful for calculating 3D traveltime and has proven to be effi...3D traveltime calculation is widely used in seismic exploration technologies such as seismic migration and tomography. The fast marching method （FMM） is useful for calculating 3D traveltime and has proven to be efficient and stable. However, it has low calculation accuracy near the source, which thus gives it low overall accuracy. This paper proposes a joint traveltime calculation method to solve this problem. The method firstly employs the wavefront construction method （WFC）, which has a higher calculation accuracy than FMM in calculating traveltime in the small area near the source, and secondly adopts FMM to calculate traveltime for the remaining grid nodes. Due to the increase in calculation precision of grid nodes near the source, this new algorithm is shown to have good calculation precision while maintaining the high calculation efficiency of FMM, which is employed in most of the computational area. Results are verified using various numerical models.展开更多
This is a continued work in studying the wave propagation in a magneto-electroelastic square column （MEESC）. Based on the analytic dispersive equation, group velocity equation and steady-state response obtained in o...This is a continued work in studying the wave propagation in a magneto-electroelastic square column （MEESC）. Based on the analytic dispersive equation, group velocity equation and steady-state response obtained in our previous paper ＇Steady-state response of the wave propagation in a magneto-electro-elastic square column＇ published in CME, the dynamical behavior of MEESC was studied in this paper. The unlimited column is an open system. The transientstate response in the open system subjected by arbitrary external fields was derived when the propagating wave pursuing method was introduced.展开更多
It is demonstrated that offshore wavenumbers of edge waves change from imaginary wavenumbers in deep water to real wavenumbers in shallow water. This finding indicates that edge waves in the offshore direction exist a...It is demonstrated that offshore wavenumbers of edge waves change from imaginary wavenumbers in deep water to real wavenumbers in shallow water. This finding indicates that edge waves in the offshore direction exist as evanescent waves in deep water and as propagating waves in shallow water. Since evanescent waves can stably exist in a limited region while propagating waves cannot, energy should be released from nearshore regions. In the present study, the instability region is predicted based on both the full water wave solution and the shallow-water wave approximation.展开更多
基金supported by National Natural Science Foundation of China under Grant No.10475009partly by the New Century Excellent Talents in University of China
文摘Stable propagating waves and wake fields in relativistic electromagnetic plasma are investigated. The incident electromagnetic field has a finite initial constant amplitude meanwhile the longitudinal momentum of electrons is taken into account in the problem. It is found that in the moving frame with transverse wave group velocity the stable propagating transverse electromagnetic waves and longitudinal plasma wake fields can exist in the appropriate regime of plasma.
基金supported by the National Key Research and Development Program(Grant No.2024YFF0508203)the National Natural Science Foundation of China(Grant No.52378475)the Science and Technology Innovation Special Project of Xiongan New Area,National Key R&D Program(Grant No.2025XAGG0056)。
文摘To address the complex seismic response of long tunnels longitudinally crossing heterogeneous geological formations,this study proposes a three-dimensional SV-wave oblique-incidence input method that accounts for the initial disturbance of the wave field induced by geological heterogeneity.The method transforms equivalent twodimensional free-field responses into equivalent nodal forces applied at the boundaries of a 3D numerical model.A longitudinally heterogeneous“hard-soft-hard”site and tunnel system is established,in which the surrounding rock is modeled using the Mohr-Coulomb constitutive law,while the concrete lining is described by the concrete damaged plasticity model.The deformation patterns and failure mechanisms of the site-tunnel system under SV-wave excitation are systematically investigated.The results indicate that seismic damage under SV-wave loading is mainly concentrated in the soft-rock region.Failure of the soft surrounding rock induces pronounced sliding of the overlying hard rock,and the tunnel suffers severe damage due to the combined effects of soft-rock failure and strong ground shaking.Parametric analyses further show that smaller impedance ratios,larger soft-rock widths,and larger incidence angles significantly intensify the seismic response of the tunnel.The findings of this study provide valuable insights for the seismic design of tunnels crossing longitudinally heterogeneous geological formations.
基金funded by the National Key Research and Development Program of China-2023 Key Special Project(Grant No.2023YFC2907400)the Hunan Provincial Natural Science Foundation for Distinguished Young Scholars(Grant No.2023JJ10072)the Science and Technology Innovation Program of Hunan Province(Grant No.2022RC1173).
文摘In mining engineering,dynamic loads acting on the surrounding rock induce irreversible damage.The damage is further exacerbated by water exudation from filling bodies or groundwater in the surrounding rock.Understanding the propagation and energy characteristics of stress waves in damaged surrounding rock is essential for improving the stability of underground structures.Hence,in this study,an improved triaxial Split Hopkinson Pressure Bar(SHPB)testing system was used to prepare four sets of impact-damaged and water-soaked specimens with varying length-to-diameter ratios in the laboratory,followed by dynamic triaxial compression testing.Test results indicate that,following dynamic impact and water soaking,the propagation of stress waves in rock is altered.Compared with intact specimens,impact-damaged and water-soaked specimens(IDWS)show a reduction in both transmission and reflection coefficients,thereby enhancing their energy absorption capacity and decreasing transmitted and reflected energy.The length(length-to-diameter ratio)of the specimen and the peak of the incident wave also affect stress wave propagation.Under the same incident peak value,the transmission coefficient increases with larger length-to-diameter ratios,whereas the reflection coefficient decreases.Similarly,the energy carried by the stress wave is influenced by specimen length:as the length grows,the energy absorbed per unit volume declines.When using energy absorbed per unit volume to characterize the dynamic triaxial strength of rock,the length-to-diameter ratio effect on strength is not pronounced.
文摘Most existing path planning approaches rely on discrete expansions or localized heuristics that can lead to extended re-planning,inefficient detours,and limited adaptability to complex obstacle distributions.These issues are particularly pronounced when navigating cluttered or large-scale environments that demand both global coverage and smooth trajectory generation.To address these challenges,this paper proposes a Wave Water Simulator(WWS)algorithm,leveraging a physically motivated wave equation to achieve inherently smooth,globally consistent path planning.In WWS,wavefront expansions naturally identify safe corridors while seamlessly avoiding local minima,and selective corridor focusing reduces computational overhead in large or dense maps.Comprehensive simulations and real-world validations-encompassing both indoor and outdoor scenarios-demonstrate that WWS reduces path length by 2%-13%compared to conventional methods,while preserving gentle curvature and robust obstacle clearance.Furthermore,WWS requires minimal parameter tuning across diverse domains,underscoring its broad applicability to warehouse robotics,field operations,and autonomous service vehicles.These findings confirm that the proposed wave-based framework not only bridges the gap between local heuristics and global coverage but also sets a promising direction for future extensions toward dynamic obstacle scenarios and multi-agent coordination.
基金the National Natural Science Foundation of China (Grant No. 10872164)the Scientific Research Foundation for the Returned Overseas Chinese Scholars, State Education Ministry (Grant No. 220542)+1 种基金the Key Project of Shanxi Education Committee (Grant No.05JK271)the Scientific Research Foundation of Xi’an University of Technology (Grant No.210532).
文摘Convection in a horizontal fluid layer heated from below is one of models for studying patterns of convection in binary fluid mixtures and has been extensively studied. In this article, the convection structures in a rectangular cell were investigated for the aspect-ratio Г= 12 and the separation ratio ψ = -0.47. Simulations were preformed by solving the hydrodynamic equations using the SIMPLE method. A Counter Propagating Wave （CPW） state was found in binary fluid convection with a periodically horizontal motion of defects, and the pattern dynamics was further discuss.
基金the National Natural Science Foundation of China(Grant Nos.50974081,50774051, 51034003)the Foundation for the Author of National Excellent Doctoral Dissertation of PR China(Grant No.200958)+1 种基金the Program for Changjiang Scholars and Innovative Research Team in University(Grant No.IRT0843)the Open Research Fund Program of the State Key Laboratory of Coal Resources and Safe Mining(China University of Mining and Technology, Beijing)(No.2007-07)
文摘To address the problem of subdividing inflexible rectangular grid models and their poor definition of velocity interfaces,we propose a complex structure triangular net for a minimum traveltime ray tracing global algorithm.Our procedure is：（1） Subdivide a triangle grid based on the Delaunay triangular subdivision criterion and the relationships of the points,lines,and the surfaces in the subdividing area.（2） Define the topology relationships and related concepts of triangular unit ray tracing.（3） The source point and wave arrival points at any time compose the propagating plane wave and the minimum traveltime and secondary source positions are calculated during the plane wave propagation.We adopt the hyperbolic approximation global algorithm for secondary source retrieving.（4） By minimum traveltime ray tracing,collect the path from receiver to source points with the neighborhood point＇s traveltime and the direction of the secondary source.Numerical simulation examples are given to test the algorithm.The results show that the triangular net ray tracing method demonstrates model subdivision flexibility,precise velocity discontinuity interfaces,and accurate computations.
文摘The dynamical response of spin-S(S=1, 3/2, 2, 3) Ising ferromagnet to the plane propagating wave, standing magnetic field wave and uniformly oscillating field with constant frequency are studied separately in two dimensions by extensive Monte Carlo simulation. Depending upon the strength of the magnetic field and the value of the spin state of the Ising spin lattice two different dynamical phases are observed. For a fixed value of S and the amplitude of the propagating magnetic field wave the system undergoes a dynamical phase transition from propagating phase to pinned phase as the temperature of the system is cooled down. Similarly in case with standing magnetic wave the system undergoes dynamical phase transition from high temperature phase where spins oscillate coherently in alternate bands of half wavelength of the standing magnetic wave to the low temperature pinned or spin frozen phase. For a fixed value of the amplitude of magnetic field oscillation the transition temperature is observed to decrease to a limiting value as the value of spin S is increased. The time averaged magnetisation over a full cycle of the magnetic field oscillation plays the role of the dynamic order parameter. A comprehensive phase boundary is drawn in the plane of magnetic field amplitude and dynamic transition temperature. It is found that the phase boundary shrinks inwards for high value of spin state S.Also in the low temperature(and high field) region the phase boundaries are closely spaced.
文摘Theoretical description of the wave propagation in an elliptical cylinder multilayer structure under the conditions of H polarization and E polarization is presented. A transfer matrix method has been developed for elliptical cylinder waves. The formulas of reflection and transmission coefficients for an elliptical cylinder multilayer structure are driven. Reflection and transmission coefficients of elliptical cylinder waves by a single elliptical cylinder interface is presented. The obtained formulas can be generalized to the cold plasma filled structures and thus the obtained results in the limit of circular cylinder structures are investigated.
基金Supported by the National Natural Science Foundation of China under Grant Nos 41331067,41474125,41274144,41174124 and 41121003the National Basic Research Program of China under Grant Nos 2013CBA01503 and 2012CB825602the Key Research Program of Chinese Academy of Sciences under Grant No KZZD-EW-01-4
文摘By performing one-dimensional （l-D） hybrid simulations, we analyze in detail the parametric instabilities of the Alfv^n waves with a spectrum in a low beta plasma. The parametric instabilities experience two stages. In the first stage, the density modes are excited and immediately couple with the pump Alfv6n waves. In the second stage, each pump Alfv^n wave decays into a density mode and a daughter Alfv6n mode similar to the monochromatic cases. Ftlrthermore, the proton velocity beam will also be formed after the saturation of the parametric instabilities. When the plasma beta is high, the parametric decay in the second stage will be strongly suppressed.
基金financially supported by National Natural Science Foundation of China(Grant Nos.52378401,52278504)the Fundamental Research Funds for the Central Universities(Grant No.30922010918)。
文摘Traffic engineering such as tunnels in various altitudinal gradient zone are at risk of accidental explosion,which can damage personnel and equipment.Accurate prediction of the distribution pattern of explosive loads and shock wave propagation process in semi-enclosed structures at various altitude environment is key research focus in the fields of explosion shock and fluid dynamics.The effect of altitude on the propagation of shock waves in tunnels was investigated by conducting explosion test and numerical simulation.Based on the experimental and numerical simulation results,a prediction model for the attenuation of the peak overpressure of tunnel shock waves at different altitudes was established.The results showed that the peak overpressure decreased at the same measurement points in the tunnel entrance under the high altitude condition.In contrast,an increase in altitude accelerated the propagation speed of the shock wave in the tunnel.The average error between the peak shock wave overpressure obtained using the overpressure prediction formula and the measured test data was less than15%,the average error between the propagation velocity of shock waves predicted values and the test data is less than 10%.The method can effectively predict the overpressure attenuation of blast wave in tunnel at various altitudes.
基金Project supported by the Chilean National Agency for Research and Development(ANID)through Grants ANID FONDECYT Regular(Nos.1211310 and 1250496)ANID Anillo de Tecnologia(No.ACT240015)the Polish National Science Centre(NCN)through Grant Agreement(No.2021/41/B/ST8/04492)。
文摘The acoustic wave propagation in gas-saturated double-porosity materials composed of a microporous matrix and mesopores with arrays of plate-type resonators is investigated.A macroscopic description,established with the two-scale asymptotic homogenization method,evidences the combined effect of inner resonances on the acoustic properties of the respective effective visco-thermal fluid.One type of resonance originates from strong pore-scale fluid-structure interaction,while the other one arises from pressure diffusion.These phenomena respectively cause weakly and highly damped resonances,which are activated by internal momentum or mass sources,and can largely influence,depending on the material's morphology,either the effective fluid's dynamic density,compressibility,or both.We introduce semi-analytical models to illustrate the key effective properties of the studied multiscale metamaterials.The results provide insights for the bottom-up design of multiscale acoustic metamaterials with exotic behaviors,such as the negative,very slow,or supersonic phase velocity,as well as sub-wavelength bandgaps.
文摘The southern part of East Siberia(SES)is highly vulnerable to flooding caused by the extreme precipitation events(EPEs)during summer.Building on previously detected EPEs in SES and Mongolia,we examined wave propagation patterns for two periods:1982-98 and 1999-2019.Our analysis revealed distinct wave train configurations and geopotential anomalies preceding EPEs,with an increase in wave activity flux across the Northern Hemisphere,followed by a subsequent decrease during EPEs.Consequently,Eastern Siberia has experienced a significant rise in wave activity.Based on geopotential anomalies over Central Siberia accompanying EPEs,we identified two main types.The first,the ridge type,is predominant during the first period and features a meridional contrast with a positive geopotential(and temperature)anomaly over Central Siberia and a negative anomaly over the subtropical regions along the same longitude.The second type,termed the trough type,is more typical for the second period.It involves either a negative geopotential anomaly or the zonal proximity of positive and negative geopotential anomalies over Central Siberia.The trough type,marked by zonally oriented anomalies in geopotential and temperature,results in a more pronounced temperature decrease before EPEs and significant zonal temperature contrasts.Further,it is related to more stationary waves over Northern Eurasia,with persistent positive geopotential anomalies over Europe linked to quasi-stationary troughs over Central Siberia and positive anomalies east of Lake Baikal.Our findings align with shifts in boreal summer teleconnection patterns,reflecting significant changes in wave propagation patterns that have occurred since the late 1990s.
基金support from the National Natural Science Foundation of China(Grant No.12172040)is acknowledged.
文摘In this paper,enhanced near-field shock wave propagation in underwater explosion is achieved by introducing a fragile air-tube under the explosive.Firstly,based on the ALE algorithm in the ANSYS/LS-DYNA software,a numerical model integrating the water,the air,the explosive,and the air-tube is developed.Comparative discussion for explosion with air-tube in the air,as well as explosion in the water without air-tube,is made to highlight the distinct energy attenuation mechanism due to the introduction of the air-tube.Then,the influence of the tube geometry,as well as evolving structural boundaries,on the explosive process is discussed exhaustively.The results indicate that the air-tube acts as a shock focusing apparatus,significantly altering explosion flow dynamics.Tube damage mode relies on tube geometrical size.Time-refreshed structural boundary affects the position the fluid flowing into the air-tube,which in turn plays an impact on the bubble pattern and energy distribution near the tube outlet.Enhanced outlet pressure is strengthened along with the decrease of the outlet radius,cross-section height ratio and tube thickness.These insights offer valuable guidance for optimizing underwater explosion and possess prospectively scientific and practical significance.
基金supported by National Key Research and Development Program of China(No.2022YFF0800602)Guangdong Provincial Key Laboratory of Geophysical High-resolution Imaging Technology(No.2022B1212010002)Shenzhen Science and Technology Program(No.KQTD20170810111725321).
文摘Global acoustic simulations are significant in revealing the internal and physical structure of the Earth.However,due to the limited flexibility of grids and the difficulties in handling boundaries,the traditional finite-difference method(FDM)is usually less used in global simulations.Nevertheless,these issues can be well resolved by employing a multi-block structured grid to discretize circular regions.In this paper,we propose an O-H grid approach to partition the circular region and utilize the curvilinear grid finite-difference method(CGFDM)to solve the acoustic wave equation within this circular domain.By appropriately stretching the grid,the interconnections between each grid block are sufficiently smooth for stable information exchange.To verify the efficacy of this method,we conducted three numerical experiments,by comparing results with alternative approaches.Our test results demonstrate good agreement between our findings and the reference solutions.Since the proposed algorithm can effectively solve wave propagation problems in circular regions,it can contribute to 2D global simulation,particularly in interpreting the Earth’s interior.
基金supported by the National Natural Science Foundation of China(Grant Nos.52178515 and 12472399)。
文摘With the application of hypervelocity weapons in warfare,comprehensively evaluating their destructive effects is of particular interest for protective engineering.Existing studies mostly focused on the depth of penetration by hypervelocity projectile,while investigation on stress waves associated with hypervelocity penetration was very limited.To clarify the generation and propagation of stress waves in concrete targets induced by hypervelocity projectile penetration,in the present study,six spherical projectile penetration tests on concrete targets were firstly conducted with projectile velocity ranged from 1875 m/s to 3940 m/s,in which the stress waves were carefully measured by the PVDF transducers.Then corresponding numerical models were developed and validated,and based on the validated numerical model the mechanisms of generation and propagation of stress waves were clarified.It was found that the stress waves observed during hypervelocity penetration are generated by the continuous interactions of projectile and target during penetration,and have unique characteristics such as the directionality and the"two peaks"phenomenon when compared with the stress waves generated by charge explosion.Finally,the effects of projectile velocity,projectile material,and target strength on the stress waves below the penetration depth we re numerically investigated,and two important indexes for evaluating the stress waves by hypervelocity penetration were proposed.
基金The National Natural Science Foundation of China under contract No.42276169。
文摘Coastal near-inertial waves are usually generated by storms passing offshore and/or nearshore,and modified by the presence of the coast.They can modify coastal currents and upper-layer velocity structures,thereby affecting material transport and ecosystem processes in the coastal region.The propagation characteristics of coastal near-inertial waves(CNIWs)are investigated in this study by using the Regional Ocean Circulation Modelling System(ROMS)model,forced by wind fields incorporating an idealized wind model around the typhoon center and ERA5 wind reanalysis data from ECMWF(European Center of Meteorological Weather Forecasting)beyond the typhoon center,and with realistic bathymetric data near the Guangdong coast,China.Spatial coherence analysis reveals that near-inertial energy propagates shoreward and upward along middle layers,guided by the topography.Near the coast,energy is transmitted offshore due to the presence of the coastal wall.Calculations of energy transport flux and group velocity further elucidate the wave propagation patterns,showing that near-inertial energy propagates onshore during the typhoon passage and offshore afterward.A two-layer structure of energy flux,separated by the thermocline,is identified,with variations observed between successive inertial periods.The sensitivity of CNIWs’propagation to typhoon parameters is examined through 12 experiments.A 10%increase in maximum wind velocity(V_(max)),radius of maximum wind(R_(max)),and typhoon translation speed()lead to respective changes in energy flux(−5%to+25%)and group velocity(−1%to+0.4%),highlighting their impacts on the CNIWs’energy fluxes.This study is of importance to coastal dynamics and disaster management.
基金supported by the National Key R&D Program of China (No.2022YFC3004602)the National Natural Science Foundation of China (No.52325404)the Shenzhen Science and Technology Program (No.JCYJ20220818095605012).
文摘Rock discontinuities such as joints widely exist in natural rock masses,and wave attenuation through rock masses is mainly caused by discontinuities.The displacement discontinuity model(DDM)has been widely used in theoretical and numerical analysis of wave propagation across rock discontinuity.However,the circumstance under which the DDM is applicable to predict wave propagation across rock discontinuity remains poorly understood.In this study,theoretical analysis and ultrasonic laboratory tests were carried out to examine the theoretical applicability of the DDM for wave propagation,where specimens with rough joints comprising regular rectangular asperities of different spacings and heights were prepared by 3D printing technology.It is found that the theoretical applicability of the DDM to predict wave propagation across rock discontinuity is determined by three joint parameters,i.e.the dimensionless asperity spacing(L),the dimensionless asperity height(H)and the groove density(D).Through theoretical analysis and laboratory tests,the conditions under which the DDM is applicable are derived as follows:and,.With increase in the groove density,the thresholds of the dimensionless asperity spacing and the dimensionless asperity height show a decreasing trend.In addition,the transmission coefficient in the frequency domain decreases with increasing groove density,dimensionless asperity spacing or dimensionless asperity height.The findings can facilitate our understanding of DDM for predicting wave propagation across rock discontinuity.
基金supported by NSFC(Nos.41274120,41404085,and 41504084)
文摘3D traveltime calculation is widely used in seismic exploration technologies such as seismic migration and tomography. The fast marching method （FMM） is useful for calculating 3D traveltime and has proven to be efficient and stable. However, it has low calculation accuracy near the source, which thus gives it low overall accuracy. This paper proposes a joint traveltime calculation method to solve this problem. The method firstly employs the wavefront construction method （WFC）, which has a higher calculation accuracy than FMM in calculating traveltime in the small area near the source, and secondly adopts FMM to calculate traveltime for the remaining grid nodes. Due to the increase in calculation precision of grid nodes near the source, this new algorithm is shown to have good calculation precision while maintaining the high calculation efficiency of FMM, which is employed in most of the computational area. Results are verified using various numerical models.
基金supported by the National Natural Science Foundation of China(No.10572001).
文摘This is a continued work in studying the wave propagation in a magneto-electroelastic square column （MEESC）. Based on the analytic dispersive equation, group velocity equation and steady-state response obtained in our previous paper ＇Steady-state response of the wave propagation in a magneto-electro-elastic square column＇ published in CME, the dynamical behavior of MEESC was studied in this paper. The unlimited column is an open system. The transientstate response in the open system subjected by arbitrary external fields was derived when the propagating wave pursuing method was introduced.
基金financially supported by the National Natural Science Foundation of China (Grant No. 51209081)China Postdoctoral Science Foundation (Grant No. 2012M511191)+3 种基金the Qinglan Project and 333 Project of Jiangsu Province (Grant No. BRA2012130)the National Key Basic Research Development Program of China (973 Program, Grant No. 2010CB429002)the 111 Project (Grant No. B12032)the Basic Research Funds for the Central Universities (Hohai University 2012B06514)
文摘It is demonstrated that offshore wavenumbers of edge waves change from imaginary wavenumbers in deep water to real wavenumbers in shallow water. This finding indicates that edge waves in the offshore direction exist as evanescent waves in deep water and as propagating waves in shallow water. Since evanescent waves can stably exist in a limited region while propagating waves cannot, energy should be released from nearshore regions. In the present study, the instability region is predicted based on both the full water wave solution and the shallow-water wave approximation.
